Optical fibers allow the distribution of time and frequency reference signals with orders of magnitude of improved resolution with respect to satellite techniques and enable to compare atomic clocks at their ultimate uncertainty. For this reason, several European laboratories are cooperating to develop a common metrological infrastructure based on the optical fiber network already in place for classical telecommunication. INRIM has developed the Italian Quantum Backbone, a 1800 km infrastructure that provides several research facilities on the Country with time/frequency services and is used as a testbed to develop novel technologies. Among the most recent results, we demonstrated how coherent laser interferometry, the technique at the heart of frequency dissemination, can improve advanced Quantum Key Distribution protocols and enable the remote sensing of earthquakes. Since 2021, the IQB is connected to the Metrological Institutes of France, UK and Germany, and INRIM took part in most recent atomic clock comparison campaigns.